This invention relates to the art of pipe wrenches and more particularly, to improvements in pivoting jaw pipe wrenches.
Pivoting jaw pipe wrenches are known as shown, for example, in U.S. Pat. No. 2,028,406 to Mead and U.S. Pat. No. 2,559,973 to Kunz. Such wrenches typically include a handle having a fixed toothed jaw at one end thereof and a toothed jaw member pivotally mounted on the one end for displacement toward and away from the fixed jaw. The pivotal jaw member has teeth thereon which are cooperable with the teeth on the fixed jaw to grip a pipe or other workpiece therebetween, and the pivotal jaw is spring biased toward the fixed jaw to provide a closing force against the pipe or workpiece therebetween. In the Mead patent, the teeth on the fixed jaw extend in an arcuate path therealong and the pivotal jaw is provided with two sets of teeth which are at an obtuse angle relative to one another and which are spaced apart along the jaw. Each set of teeth on the pivotal jaw is cooperable with a different portion of the teeth on the fixed jaw to grip a square or round object therebetween. In the Kunz patent, the teeth on the fixed jaw extend along an arcuate face thereof and the pivotal jaw comprises a pair of legs at substantially right angles to one another and provided with corresponding sets of teeth. A pipe to be gripped by the wrench is cradled between the legs of the pivotal jaw and is urged against the fixed jaw to provide three point contact between the wrench jaws and pipe.
Pivoting jaw wrenches are desirable in that they are quickly applied to a workpiece to be gripped and turned, such as a pipe or pipe coupling and are self-adjusting to the size of the workpiece. However, the gripping capability of such wrenches is compromised when a large range of pipe sizes are required to be gripped while limiting the rotational swing of the pivotal jaw to 90xc2x0 to facilitate operability of the wrench. In this respect, a large range of pipe sizes and the limitation of a 90xc2x0 swing of the pivotal jaw results in undesirable slippage between the wrench and pipe in connection with the turning of larger sizes of pipe such as 1xc2xd inches to 2 inches and larger diameter pipe. Further in this respect, a line from the pivot axis of the pivotal jaw to a given point on the arcuate jaw face and from the latter point through the vertex between the sets of teeth on the pivotal jaw provides a camming angle for a given diameter pipe and, in many pivoting jaw wrenches heretofore provided, the camming angle becomes unfavorable on the larger sizes of pipes which results in inefficient gripping performance, slippage and potential damage to the workpiece as well as the teeth on the jaws of the wrench.
In accordance with the present invention, a pivoting jaw pipe wrench is provided by which improved gripping performance is achieved with respect to a large range of pipe sizes which could not be satisfactorily accommodated in a single pivoting jaw wrench heretofore available. More particularly in this respect, improved gripping performance is achieved by providing a discrete tooth on the fixed jaw for each different size pipe to be gripped by the wrench while maintaining a functional pivot angle of 90xc2x0 for the pivotal jaw. With regard to the latter, the working angle for the wrench is 90xc2x0 and the actual angle is about 98xc2x0 to provide an allowance for over travel. Further, an optimum camming angle is maintained for a given discrete tooth and pipe size combination and, preferably, each discrete tooth has a preferred included angle and preferred rake and relief angles relative to a diametrical line through the pipe and the apex of the tooth. The provision of a discrete tooth for each different pipe diameter together with a preferred camming angle for the tooth results in improved gripping performance relative to similar wrenches heretofore available, and the provision of a specific orientation of the tooth relative to the center of the corresponding pipe to be gripped and specific rake and relief angles for the tooth further improves the gripping performance.
In connection with a series of pipes having nominal diameters between xe2x85x9c inch and 2 inches, and a pivotal jaw having a working pivot angle of displacement of 90xc2x0 between the closed and open positions thereof, an improved gripping performance is achieved with a camming angle maintained between 90xc2x0 and 150xc2x0 for each of the discrete teeth provided on the arcuate jaw face for the different diameter pipes. Further, optimum gripping performance is realized when the discrete teeth for camming angles between 131xc2x0 and 150xc2x0 have an included angle of 90xc2x0, a relief angle of 40xc2x0 and a rake angle of xe2x88x9240xc2x0. Likewise, optimum gripping performance is achieved when the discrete teeth providing camming angles between 90xc2x0 and 130xc2x0 have an included angle of 55xc2x0, a relief angle of 25xc2x0, and a rake angle of 10xc2x0. An acceptable range for each of the included, relief and rake angles is xc2x15xc2x0.
It is accordingly an outstanding object of the present invention to provide a pivoting jaw pipe wrench which accommodates a large range of pipe sizes and provides improved gripping performance with respect thereto relative to pivoting jaw pipe wrenches heretofore available.
Another object is the provision of a wrench of the foregoing character wherein the fixed jaw face comprises a plurality of discrete teeth therealong, one for each different size pipe to be accommodated.
Still another object is the provision of a wrench of the foregoing character wherein the camming angle for each discrete tooth with the corresponding pipe gripped between the latter tooth and the pivotal jaw member is between 90xc2x0 and 150xc2x0.
A further object is the provision of a wrench of the foregoing character wherein each of the discrete teeth has a specific orientation, included angle, rake angle, and relief angle relative to the pipe corresponding thereto when the pipe is gripped by the wrench.
Yet another object is the provision of a wrench of the foregoing character wherein, for camming angles greater than 130xc2x0, a discrete tooth has a 90xc2x0 included angle, a relief angle of 40xc2x0, and a rake angle of xe2x88x9240xc2x0, and, for camming angles between 90xc2x0 and 130xc2x0, a discrete tooth has an included angle of 55xc2x0, a relief angle of 25xc2x0, and a rake angle of 10xc2x0, with each angle having an acceptable range of xc2x15xc2x0.